Characterization of Gel16 as a cytochrome P450 in geldanamycin biosynthesis and in - silico analysis for endogenous electron transport system.

Geldanamycin and its derivatives, inhibitor of heat shock protein 90, are considered as potent anticancer drug, and their biosynthetic pathway has not yet been fully elucidated. The key step of conversion of 4,5-dihydrogeldanamycin to geldanamycin was expected to catalyse by a P450 monooxygenase, Gel16. The adequate bioconversions by cytochrome P450 mostly rely upon its interaction with redox partners. Several numbers of ferredoxin and ferredoxin reductase are available in a genome of organism, but only few suitable partners can operate in full efficiency. In this study we have expressed cytochrome P450 gel16 in Escherichia coli and performed the in-vitro assay using 4,5-dihydrogeldanamycin as a substrate. We demonstrated that in-silico method can be applicable for the efficient mining of convenient endogenous redox partners (9 ferredoxins and 6 ferredoxin reductases) against CYP Gel16 from Streptomyces hygroscopicus . The distances about ligand FDX4-FDR6 were found to be 9.384 Å. Similarly the binding energy between Gel16-FDX4 and FDX4-FDR6 were -611.88 kcal/mol and -834.48 kcal/mol, respectively, suggesting the lowest distance and binding energy rather than other redox partners. These findings suggested that the best redox partners of Gel16 could be NADPHFDR6FDX4Gel16.